U.S. Pat. No. 3,429,298 issued Feb. 25, 1969 discloses a poultry house and an associated curtain raiser which includes an electric motor controlled by a relay, a thermostat and a timer to operate the building curtains through a system of controlled cables.
U.S. Pat. No. 4,605,162 issued Aug. 12, 1986 discloses a bimetal strip mounted to a mechanical arm and inserted into a power resistor used as a heater. In arrangements of this type, the time delay following power failure cannot be determined with any degree of accuracy and the energy required is substantial.